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Nov 26, 2013

Vitamin D Supplements Fail to Improve Blood Pressure

Clinical trial cut short after finding no association between vitamin D supplements and blood pressure control.

Roughly one-third of Americans don’t get enough vitamin D—an important nutrient that aids in the absorption of calcium to build strong bones. Vitamin D was also believed to promote healthy blood pressure until researchers shared their latest study findings at the American Heart Association Scientific Sessions in Dallas.

Referred to as the DAYLIGHT Study (Vitamin D therapy in individuals at high risk of hypertension), this clinical trial studied the effects of vitamin D supplements on blood pressure. A total of 363 patients with high blood pressure participated in the study, each of which was randomly assigned to take low-dose (400 iU/d) or high-dose (4,000 iU/d) vitamin D supplements daily.

After just six months, the study was cut short because there was no significant difference in the blood pressure levels of participants. To put it simply, the treatment was ineffective.

Based on these findings, authors believe that the relationship between vitamin D and blood pressure is not causal. In other words, low levels of vitamin D may be associated with high blood pressure, but low vitamin D levels don’t cause high blood pressure.

Vitamin D can be found in foods like eggs and fish but our bodies can also produce vitamin D when we’re exposed to sunlight. Therefore, it’s possible that patients with higher vitamin D levels are healthier than those with lower levels, which may explain the link between vitamin D levels and blood pressure. For example, a person who eats plenty of heart-healthy fish and exercises outdoors regularly would naturally have higher vitamin D levels than someone who has an unhealthy diet and sits inside all day, inactive. Although the person with higher vitamin D would likely have healthier blood pressure, it’s primarily a result of their lifestyle choices rather than their vitamin D intake.

Study findings have already made experts think twice about their understanding of vitamin D and heart health. Most of the research linking vitamin D deficiencies to high blood pressure included long-term studies that follow groups of people over time. While these types of studies are helpful, clinical trials like the DAYLIGHT study are considered the gold standard of research because the results are more reliable. These findings suggest that vitamin D shouldn’t be used as a possible treatment for high blood pressure, but future research is needed to better understand the relationship between vitamin D deficiency and hypertension.

Questions for You to Consider

  • What are good sources of vitamin D?

  • Vitamin D can be found naturally in a few food sources such as fatty fish, cheese and egg yolks. Vitamin D is also added to some food products like milk and some yogurts, juices and cereals. The best way to prevent vitamin D deficiency, however, is to get enough regular exposure to the sun and to take supplements when necessary.
  • Who is at risk for vitamin D deficiency?

  • Those at greatest risk for vitamin D deficiency include breast-fed infants, older adults, people with dark skin, people with fat malabsorption and people who are obese or have undergone gastric bypass surgery.

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